Chevy 454 Motorhome engine problems

[Buggs67]

This might be off topic but my motor home has a Chevy 454. Twice now we've been running along fine for a couple hours and it just dies.

Plenty of fresh fuel and it cranks over well.

Towed to a shop ($$$$$) each time and then after sitting overnight or a couple days it starts and runs fine. The first shop was Chevy experts and changed the fuel filter and checked the pressure. They couldn't find any problem. We've logged about 400 miles since then and it happened again.
Sounds to me like vapor lock or intermittent fuel pump failure. Any help??

I know many here are very knowledgeable in all things mechanical.

 

[bigtiller]

Plugged gas cap?.... It happens!

 

[CajunRider]

Check your fuel pump strainer sock in the fuel tank. It is likely plugged with debris and gunk. Overnight it will fill up enough for you to start but as you run the engine hard the demand will overwhelm the supply and the engine dies.

 

[flyerdan]

If it just stops without sputtering or surging, I'd suspect an electrical issue. There is a module in the distributor that is problematic, it could be that it gets hot and opens, and works normally when it cools off enough. Kind of like a thermal switch, although they mostly just quit working altogether.

 

[bigdeano]

What year is it? If it happens again pull a plug wire and use a spare plug to check for spark.

 

[kenmac]

Check your fuel pump strainer sock in the fuel tank. It is likely plugged with debris and gunk. Overnight it will fill up enough for you to start but as you run the engine hard the demand will overwhelm the supply and the engine dies.

I second this....I've had it happen.. Is this mechanical fuel pump or electric ?

 

[Buggs67]

Thanks for the input.

I should have been more specific. It's a 1999 fuel injected model in a Class A. Engine mounted between the front seats. And I assume it's an electric fuel pump.

Both times this has occurred it was on the interstate in heavy rush hour traffic. Barely out of the left lane. My family's safety was paramount concern. If I had the ability to try to diagnose the problem I'd start with some starter spray but the intake is hard to get to.

The first time I had this problem last October it stalled, I threw it in neutral and it started again. Stalled again a couple miles later, restarted, died and then wouldn't start again. My wife figured I ran out of gas, and that kind of how it felt. The garage that time (over an hour from home) changed the fuel filter (which was gunky but not awful) and checked the fuel pressure and all electrical systems. They ran it an hour in the lot and no problem.

I drove it home the long way (1 1/2 hrs) and it was fine. We drove down to PA about 4 hours in April, and it was fine.

Fresh gas in PA and 3 hours later this past Wednesday it died and wouldn't restart.

It's at the mechanic right now and it started immediately when he tried it.

 

[Stimw]

I have owned 2 of them, 1983 Winnie and 1989 Southwind class A's. (both carborated )
There is a fuel pump relay that only works with oil pressure.
BUT, when you turn on the key it will cycle for about 30 sec to allow it to start.
If you have someone turn the key on and off while you listen under the gas tank you should be able to here pump run for short periods.
It could be bad fuel pump relay or bad oil pressure sending unit. (I have had sending units fail on GM vehicles)
Just some places to look.
That 454 will keep up with traffic!
I even had the 1983 up to 85 mph (towing a 23' boat) trying to get away from a semi that kept passing me and slowing down on the next hill! That was back in the late 80's.

 

[kenmac]

I would advise to add an in cab fuel pressure gauge and keep a check on that gauge when you are having these issues.
Sounds like a fuel delivery issue to me.
Of course I'm sitting behind a computer

 

[Sawyer Rob]

I'd be looking hard at the electric fuel pump... They sometimes start to fail just that way...

Can you switch to a different tank, it will have a different pump in it?

SR

 

[kenmac]

I'd be looking hard at the electric fuel pump... They sometimes start to fail just that way...

Can you switch to a different tank, it will have a different pump in it?

SR

that's the reason I advised adding a fuel pressure gauge .. It's a 99 mod. If the fuel pump has never been replaced, It sure is suspect.

 

[MossRoad]

If its a 1999 its most likely got the throttle body fuel injection and an electric fuel pump in the tank. As others have mentioned, have them check the fuel pressure. We just had a similar incident with our 1993 Suburban, 350 with throttle body fuel injection and fuel pump in the tank. The fuel pressure was fine at idle, but towards the low side when under load. Still within specs, but on the low side. It was the original fuel pump. We changed the fuel pump and all problems went away. Its something to look at, for sure.

 

[Slowpoke Slim]

Had the same thing happen with a Ford class C and V10. With us it vapor locked. Only did it one time, but during rush hour traffic while trying to get through Salt Lake City on the interstate. Check the fuel lines, vent lines, and fuel return lines from the tank to the engine and back. That is where our problem lay.

 

[Stimw]

If its a 1999 its most likely got the throttle body fuel injection and an electric fuel pump in the tank. As others have mentioned, have them check the fuel pressure. We just had a similar incident with our 1993 Suburban, 350 with throttle body fuel injection and fuel pump in the tank. The fuel pressure was fine at idle, but towards the low side when under load. Still within specs, but on the low side. It was the original fuel pump. We changed the fuel pump and all problems went away. Its something to look at, for sure.

Not sure what system OP has.
But with your throttle body, if you have additional problems the T B has a fuel pressure regulator in it.
Pump supplies fuel, regulator determines how much fuel is returned to tank.
The regulator gets weak causing low pressure.
The regulator is not expensive and I bought one for my 1989 1500 PU at local parts store back in the 90's and it wasn't hard to change.
New pump might have boosted your pressure but you still might need new regulator.
Also, the hardest thing on ALL electric fuel pumps is running low on fuel. They need the fuel to keep cool. I try not to go under 1/4 tank with all my vehicles!

 

[not2old]

One of my old Fords would run all day if I stayed below 100 kph (60 mph ). If I went faster, after about 1/2 hour it would quit and not run on that tank until it had cooled off. Was definitely the fuel pump. because I had two tanks and am lazy, I drove it that way for years.

 

[kenmac]

If its a 1999 its most likely got the throttle body fuel injection and an electric fuel pump in the tank. As others have mentioned, have them check the fuel pressure. We just had a similar incident with our 1993 Suburban, 350 with throttle body fuel injection and fuel pump in the tank. The fuel pressure was fine at idle, but towards the low side when under load. Still within specs, but on the low side. It was the original fuel pump. We changed the fuel pump and all problems went away. Its something to look at, for sure.

If it's a 93 mod. and you are just now having to replace the FP you are very lucky. I had a 96 van that I put 2 FP's in before I sold it in 2006.

 

[MossRoad]

If it's a 93 mod. and you are just now having to replace the FP you are very lucky. I had a 96 van that I put 2 FP's in before I sold it in 2006.

It only had 46,000 miles on it when I bought it 9 years ago. Has 123,000 now. Pump failed around 120,000. It was a former emergency services truck for a local fire department, hence the low miles. Rust has taken over the body, however, so its on its last legs, or skins, I should say. Frame is still good.

 

[Egon]

The vapour lock idea sounds good to me.

As mentioned a fuel pressure gauge sounds reasonable.

 

[Mace Canute]

I had to replace the fuel pump on my 1994 Chevy 3/4 ton and had to also replace the fuel pump relay which had an obviously bad contact once I pulled it apart. I would suspect a bad fuel pump first since mine was doing exactly what yours is doing.

Hooking up an auxiliary fuel pressure gauge isn't easy to do since you need specific fittings to install a tap inline and your plumbing for it needs to be capable of handling the pressure. If you manage to make such a hook up, never run the fuel line into the interior of your motor home; a failure of the line or gauge will result in gasoline being sprayed around with the resulting potential of a very serious fire bomb going off with an inadvertent source of ignition.

 

[spokane 1]

This might be off topic but my motor home has a Chevy 454. Twice now we've been running along fine for a couple hours and it just dies.

Plenty of fresh fuel and it cranks over well.

Towed to a shop ($$$$$) each time and then after sitting overnight or a couple days it starts and runs fine. The first shop was Chevy experts and changed the fuel filter and checked the pressure. They couldn't find any problem. We've logged about 400 miles since then and it happened again.
Sounds to me like vapor lock or intermittent fuel pump failure. Any help??

I know many here are very knowledgeable in all things mechanical.

I assume this is a carburated motorhome? The first thing Id check is carburation boil over. If I remember years ago the Q-jet carb had a serious problem of taking on to much heat.
this is caused by a exhaust expansion crossover inside the intake manifold.

Motorhomes are so tight inside the engine housing and they simply run hot.......

Its very difficult to see but under most Q-jets they placed a heat shield its like a chrome shield sandwiched in with the base plate gasket.. to ward off heat from the intake manifold.
when the vehicle gets a carb rebuild ..mechanics with little "old day schooling" toss the heat shield thinking its a funky gasket. (this is when all the problems begin)

what happens the rig runs great for miles hits a hill them the gas boils over inside the carb.........one has to sit patiently for 1/2 hour
with no chance of restart and flooded conditions. then after its cool it starts right up and shows no symptoms.